Telephone relay apparatus



(No Model.) W. L. RICHARDS. TELEPHONB RELAY APPARATUS.

Patented July 16 r .cation.

Whentelephone-lines are of extremelength,

UN rrnn TATES ATENT @FFICE \VILTON L. RICHARDS, OF MALDEN, ASSIGNOR TOTHE AMERICAN BELL TELEPHONE COMPANY, OF BOSTON, MASSACHUSETTS.

TELEPHONE RELAY APPARATUS.

SPECIFICATION forming part of Letters Patent No. 542,657, dated July 16,1895.

Application filed March 16, 1895- Serial No. 542,030. (No model.)

residing at Malden, in the county of Middlesex and State ofMassachusetts, have invented certain Improvements in Telephone RelayApparatus, of which the following is a specifiitis convenient to dividethem at an intermediate station and to interpose some form of relayapparatus between the two sections or circuits, wherebythevoice-currents developed by the transmitter at either end station,instead of being necessitated to travel the entire line and ultimatelyin an enfeebledcondition to operate thereceiver at the other end stationdirectly, are enabled to put in operation a fresh source of electricalenergy located at the intermediate or central station, thecomparatively-strong current of which may then traverse the remainingportion of the said long line for the operation of the said telephone atthe receiving-station.

My present invention relates to such an organization, and particularlyto the mode adopted for rendering the relay-magnet of each of the twolines concerned null with respect to any currents developed by its ownaction in the other, which currents otherwise are prone to'react on thesaid relay and to produce and perpetuate musical sounds manifestingthemselves in and by means of the several receivers in circuit.

Telephonic relays have frequently been devised which act in onedirection, but this invention permits of reciprocal transmission andaccomplishes the change of direction automatically-that is to say,without the aid of switches of any kind.

Myinvention consists in combiniuga recip rocal telephone-relay withartificial balancingcircuits in such manner that when either line istransmitting the receiving-magnet thereof, while remaining fullyresponsive to such transmission, is made null or irresponsive to therelayed transmission of the receiving-line, so that its operation is notconfused by reactionary effects.

It further consists in associating with the two main circuits at thecentral or intermediate station two artificial balancing-circuits ofsuitable resistance and capacity, one for each main circuit; a relayelectromagnet or receiving-magnet for each line, having its coils partlyin the main circuit and partly in the balancing-circuit; an inductioncoil for each main circuit, having its secondary Winding in a section ofconductor common to both main and artificial circuits, so that it isenabled to supply current to both in differentdirections through thesaid relay, which thereby is made neutral to outgoing-currents; and twolocal transmitting or relay circuits, including each a suitable sourceof current, such as a battery, a variable resistance medium, and theprimary winding of an induction-coil, these two last appliances being sorelatively disposed that the primary winding of the induction-coil ofeach circuit is connected up with a variable resistance or transmittingmedium controlled or operated bytthe relay or receiving magnet of theother circuit.

In the drawings, Figure 1 is a diagram of two completetelephone-circuits fitted at an intermediate station with a repeatingapparatus. Figs. 2 and 3 are diagrams illustratingmodified arrangements'ofreceiving magnet-windings, all, however, based upon the sameprinciples; and Fig. 4: shows an arrangement in which the artificialbalancing converge to or enter the intermediate central station 0, wherethey may be united to constitute a through line of communication betweenthe stations A and B. At the said stations A and B the telephones may beconnected in the customary way, as shown at A, where thetransmitting-instrument M is included in the circuit of a localgenerator, as a battery I), and adapted to act upon the main circuitthrough the intermediation of an induction-coil I, whose primary winding19 is also in the said local circuit, and whose secondary s is in themain circuit. Both secondary and primary windings are shown as beingdivided into two sections p p and s 8 and the receiving-telephone Tisconnected in the main circuit between the two sections 5 s of ICO o ofmain circuit L the said secondary; or, if desired and convenient, thetelephones may be connected, as at B,

where the battery 11 transmitter M, and receiver T are all included inthe main circuit L At the central station O the two line-circuitsconcerned L and L have similar con nections. Each has a repeating orrelay magnet R responsive to currents coming in from the distanttransmitter of its own line, and an induction-coil 1 to serve as anintermediary for receiving the relayed currents originating tin theother line. Each main circuit is also associated with an artificialbalancingcircuit D containing a condenser, as in'Fig. 1, a condenser andresistance (preferably adjustable) in series, as in Figs. 2 and 3, or acondenser and resistance-coils in parallel, as in Fig. 4t

Referring again exclusively for the present to Fig. 1, it will be seenthat at the station Othe line-conductors 2 and3 of the main cir-: cuitsL L are united at the points 6 and 7 bya cross-conductor d, in which isconnected the secondary wire 5- of the associated induction-coil 1 andthat one bobbin of the relay-magnet R of the said circuits, respect-iively, (forming one section or half of its winding,) is contained insuch closed circuit. The

cross-conductor d of each main circuit alsoforms a part of theartificial balancing or respectively include a source of current S, or-

dinarily a battery, a variable-resistance medium an, organized to serveas a relay-transmitter, and the primary windings p ofthe two i Thevariableinduction coils respectively.

- resistance medium m of the repeating-circuit 0c is mounted inoperative relation to the relay-magnet R of main circuit L and isactuated by the varying attraction exercised by the said magnet upon itsdiaphragm orarmature g, and the primary winding 19 of the samecircuit 0cis that of the ind uction-coil 1 primary winding 19 included in thelocal repeating-circuit y,is that of the induction-coil belonging tomain circuit L, and the variable.

resistance medium 1%, connected together with it in the saidlocal-circuit wire, is placed in juxtaposition to the relay-magnet R ofmain circuit L to be operated thereby. Thus when messages are beingtransmitted from either of the stations A or B the relay-magnet of thetransmitting-circuit for the time beingsay Lexercises such a variableattraction upon its armature or diaphragm 9 that if, instead of beingorganized to repeat the message into a second circuit, it should bearranged simply as an ordinary sound-reproducing telephonereeeiver itwould emit a copy of the original In the same manner the:

sounds uttered at station A. The armaturevibration thuseffectuatedoperates the variable-resistance medium of the local circuit at,throwing the current of its battery S into fiuctuations corresponding incharacter to those originally produced in main circuit L; but the newvariations are, as it were, reinforced by the introduction of a freshbattery and are stronger than those delivered by the main circuit L atthe relay-station C. By means of the induction-coil 1 whose primarywinding is contained in the local circuit as, the Voice-currents of thissecond series are impressed upon the receiving-circuit L traversing thesame, for the operation of the receiving-telephone T at the distantstation 13; Of course when 15 transmits a corresponding but reversedoperation is performed.

When the currents of one circuit are repeated into the other by theaction of the induction-coill of the latter it is evident that they mustcirculate in the relay-magnet coils of the latter, so that, unless somemeans of prevention be adopted, the said relay-magnet will be responsiveto the relayedcurrent as well as to the currents of its own circuit, andthe efficient transmission of speech will be much impaired by theconsequent confusion. To obviate this liability I divide the relaymagnetwinding into two equal portions, and placing one half, as described, inthe workingcircuit, I place the other half in the balancing-circuit D,and as the ind uction-coil bridge connects with the main and balancingcircuits at'the point 6, between the two spools of the relay-magnet, thecurrents flowing outward from the said induction-coil split be tween thecircuits and exercise a differential effect on the relay. The said relayis null to outgoing currents, while it remains fully responsive tocurrentsdue to the operation of the transmitter of its own line.

' It is convenient and advisable to include a rheostat or adjustableresistance in the artificial balancing-circuit D, as shown in Figs. 2

'and3, so that the resistance to voice-currents between its points ofjunction 6 and 7 with the main line may be varied within wide limits.

It is also desirable in practice to perfectly balance the magnetizingvalue of the two relay-sections, and to that end I prefer the-splitcoilarrangement of Fig. 2, in which the two poles of the bipolar magnet nare each provided with two like coils. Then both the main and balancingcircuits are led successively through two of the said coils, one on eachpolar arm. The main circuit is traceable from the conductor 2' throughthe front coil h on pole n, then through the back coil h on pole s andthence to the point 6, while the balancing-circuit may betraced fromwire 5 through coil h on pole a and thence through the coil h to thepoint 6, suchan arrangement aiding materially in securing a satisfactorybalance.

Another and similar plan for the relay-magnet connection, which has beensuccessfully tried, is that shown in Fig. 3, which discloses aunipolarmagnet having a single winding 9 with the line-conductor 2,connected at one end, the balancing-circuit conductor 5 at the other,and the cross-conductor d to a point 6 at the middle.

The circuit arrangement of Fig. 4 differs from that of Fig. 1 only inthat the artificial balancing-circuit D is shown with its adjustableresistance r and its condenser c in parallel branches-that is to say,the resistance is directly in the circuit and is shunted by thecondenser, which supplies the required capacity.

Having now fully described my invention, I claim- 1. An automaticreciprocal telephone repeater or relay system, comprising two main linecircuits; each being associated with the following instrumentalities; atransmitter induction coil having its secondary winding connectedtherein; a branch circuit including acondenser shunting the saidsecondary winding; a relay magnet having a portion of its windingincluded-in the main, and the remaining portion thereof in the saidbranch circuit; and a repeating or local transmitter circuit containinga source of current, a variable resistance medium, and the primaryWinding of the said induction coil, the variable resistance connectedwith the induction coil of each main circuit, being placed injuxtaposition or operative relation to the relay magnet of the othermain circuit, to be controlled by the varying attractive power thereof;substantially as described.

2. An automatic reciprocal telephone relay or repeatenconsisting of twomain line circuits extending to outlying stations; and an artificialline or balancing circuit includinga condenser, for each; a transmittinginduction coil for each, having its secondary winding connected inparallel with the said main and balancing lines, so that it forms asection of conductor common,and supplying current to both; a relaymagnet for each, havinga split or differential winding, the two sectionsthereof being included in the main and balancing circuits'respectively;and two relay or local transmitting circuits, each containing a sourceof current, a variable resistance medium, and the primary winding of oneof the said induction coils, the variable resistance of each relaycircuit being associated with and controlled by the relay magnet of oneof the said main circuits, while its primary winding is associated withthe secondary of the induction coil of the other-main circuit;substantially as described.

connected with the receiving magnet thereof, in such manner that therelayed currents are balanced in its coils, and prevented thereby fromexercising reactive effects.

4.. The combination of two telephone main circuits converging fromdistant stations to a common terminal station; a relay magnet, and atransmitting induction coil connected with each, the relay magnet ofeach being adapted to operate a variable resistance medium in circuitwith a battery, and the primary winding of the induction coil of theother, thereby transferring messages from one to the other; and anartificial balancing circuit of suitable resistance and capacity foreach main circuit, in which a section of the relay of such main circuitis connected, whereby the said relay is prevented from responding to thecurrents impressed by its operation upon the second circuit.

5. In a telephone repeater system and apparatus, the combination of twomain telephone circuits entering a central station, and extendingtherefrom to different outlying and distant stations, both closed atsaid central station through the secondary winding of their respectiveinduction coils; and telephones at the said distant stations included inthe said main circuits; with an artificial balancing circuit for eachmain circuit connected in parallel therewith, in respect to the saidinduction coil windings, and containing suitable resistance, and acondenser; a split coil of differential relay magnet for each tele phonecircuit, having the two sections of said coil included in its associatedmain and artificial circuits respectively, whereby the effect on saidrelay magnet of relayed currents is balanced and nullified, while thesaid magnet is left fully responsive to thedistanttransmitter of its owncircuit; and two local battery circuits, each including a variableresistance medium operated by the relay magnet of one of the maincircuits,'and a primary winding acting upon the secondary winding of theinduction coilof-the other main circuit substantially as specified.

6. The combination in an automatic and re ciprocal telephone relayapparatus, of two main telephone line circuits; and two independentartificial lines or balancing circuits associated with the said maincircuits respectively; with repeating or relay electro-magnets, one foreach set of circuits, each magnet havcircuit, and one half in theassociated artificial line or balancing circuit; substantially asdescribed.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing witnesses, this 7th day of March, 1895.

WVILTON L. RICHARDS.

Witnesses:

GEO. WILLIS PIERCE, FRANK C. LooKwoon.

ing one half of its Winding in the main line its

